This invention relates to sugar-coated solid dosage forms, and more particularly to sugar-coated solid dosage forms having at least one coating layer that is provided in direct contact with the dosage body and contains a hydroxypropyl cellulose with a low degree of substitution. The invention relates also to a method for providing a sugar coating on solid dosage forms.
In general, sugar-coated solid dosage forms, such as tablets or pills, are prepared by providing successive layers of subcoating or undercoating, smoothing or middle-coating, and coloring or top coating over the body of each solid dosage form. The coating that is formed by sugar coating syrup containing gelatine as a binder tends to extend the disintegration time of the coated dosage forms with the lapse of time due to hardening of the gelatine. This fact is very remarkable when a disintegration test is carried out using a neutral medium or water as the testing fluid, while it is less significant with an acid medium, such as a simulated gastric juice.
The reason for this difference is presumably that the presence in the sugar coating of much calcium carbonate which is readily soluble in an acid medium, such as a simulated gastric juice, works to accelerate the mechanical disintegration of the coating, while it is shown in the disintegration test with a neutral medium that there take place no dissolution of calcium carbonate and hence no acceleration of disintegration, despite the tendency of extending the disintegration time by the hardening of gelatine.
It is therefore natural that such sugar-coated solid dosage forms whose disintegration time is extended in a neutral medium or water will have little or improper effect when administered by those suffering from anacidity or hypacidity.
Various methods have been proposed to solve the above-described drawbacks of the sugar-coated solid dosage forms by improving their disintegrability, especially in a neutral or aqueous medium. One method proposed is a method of sugar coating in which a dusting powder used is the subcoating step is formulated with the addition of at least one selected from sodium salts of carboxymethylated starch, metal salts of carboxymethylcellulose and guar gum, as disclosed in Japanese Patent Public Disclosure No. 49-31816, though not with completely satisfactory results.